Bellows Pump

ABSTRACT

The present invention relates to, among bellows pumps for transporting a liquid with using a bellows which axially extends and contracts, a so-called internal-liquid type bellows pump in which an air chamber is formed outside a bellows and a liquid to be transported is sucked into the bellows. In order to prevent a pump bellows, a piston or coupling plate, and a shaft coupling them from being deviated from the same axis, prolong the life period of the pump, maintain the pump performance for a long term, and realize compactification and cost reduction of the pump, an external thread is formed on the outer face of one end side of the shaft, an engagement head is formed on the other end, a bottomed cylindrical shaft screwed portion which is projected from a center portion of the bottom into the pump bellows on the same axis, and which has an internal thread on an inner face is disposed in a bottomed cylindrical pump bellow, and the one end side of the shaft is directly coupled with a center portion of the pump bellows by thread joining.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to, among bellows pumps for transporting a liquid with using a bellows which axially extends and contracts, a so-called internal-liquid type bellows pump in which an air chamber is formed outside a bellows and a liquid to be transported is sucked into the bellows.

2. Description of the Prior Art

Conventionally, a bellows pump of such a kind is used as a pump for transporting a liquid such as a chemical liquid, a solvent, or pure water in a semiconductor manufacturing factory. For example, bellows pumps of such a kind are classified into the following two categories.

The first one is a bellows pump such as disclosed in Japanese Patent Application Laying-Open No. 2001-317449. The conventional bellows pump comprises: a pump body in which suction and discharge ports for a liquid to be transported (hereinafter, referred to as transported liquid) are formed; a pump unit which is placed on one side of the pump body; and an accumulator unit which is placed on the other side of the pump body. The pump unit comprises: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to one side portion of the pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to the pump body in the axially outside of the pump bellows, a first cylinder section which is projected on the same axis as the pump bellows from the cylinder head portion toward the pump body so as to internally accommodate the pump bellows, which is opposed in an open end portion to the pump body across the open end portion of the pump bellows, and which cooperates with the cylinder head portion to form a pump air chamber outside the pump bellows, and a second cylinder section which is projected on the same axis as the pump bellows from the cylinder head portion toward the side opposite to the first cylinder section, and into which a piston is axially slidably fitted; a coupling shaft which slidably passes through a center portion of the cylinder head portion in the axial direction to couple the pump bellows with the piston; and suction side and discharge side check valves which are attached to the pump body in the pump chamber. The pump bellows, the coupling shaft, and the piston are integrally reciprocated by air which is alternately supplied to the pump air chamber and the second cylinder section. The pump bellows repeatedly extends and contracts so that, when the pump bellows extends, the transported liquid is sucked from the suction port of the pump body into the pump chamber via the suction side check valve, and, when the pump bellows contracts, the transported liquid is discharged from the discharge port of the pump body via the discharge side check valve. By contrast, the accumulator unit comprises: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to another side portion of the pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from the pump chamber via the discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside the accumulator bellows, which is opposed in an open end portion to the pump body across the open end portion of the accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside the accumulator bellows. Pulsation of the discharge pressure of the pump unit is absorbed by extension and contraction of the accumulator bellows.

The second one is a bellows pump such as disclosed in Japanese Patent Application Laying-Open No. 2002-174180. The conventional bellows pump comprises: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of the pump body, respectively. Each of the pump units comprises: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to one side portion of the pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to the pump body in the axially outside of the pump bellows, and a first cylinder section which is projected on the same axis as the pump bellows from the cylinder head portion toward the pump body so as to internally accommodate the pump bellows, which is opposed in an open end portion to the pump body across the open end portion of the pump bellows, and which cooperates with the cylinder head portion to form a pump air chamber outside the pump bellows; a coupling shaft which slidably passes through a center portion of the cylinder head portion in the axial direction to couple the one end with the pump bellows; a coupling plate which is coupled with the other end of the coupling shaft; and suction side and discharge side check valves which are attached to the pump body in the pump chamber. The coupling plates of the pump units are coupled together. Suction valve ports of the suction side check valves of the pump units are communicatingly connected to the suction port of the pump body, and discharge ports of the discharge check valves are communicatingly connected to the discharge port. The pump bellows, the coupling shafts, and the coupling plates of the pump units are integrally reciprocated in the same direction by air which is alternately supplied to the pump chambers of the pump units. The pump bellows repeatedly extend and contract in alternate manner so that, when the pump bellows of one of the pumps extends and the transported liquid is sucked from the suction port of the pump body into the pump chamber of the pump via the suction side check valve, the pump bellows of the other pump unit contracts and the transported liquid is discharged from the discharge port of the pump body via the discharge side check valve.

In both the conventional bellows pumps, flanges and bolts which are made of a metal are used in coupling of the pump bellows with the coupling shafts, and metal nuts and bolts are used in coupling of the coupling shafts with the pistons or the coupling plates.

In order to eliminate contamination caused by metal ions and minimize contamination of a transported liquid due to a pump, a countermeasure to form components by a resin is advancing. In some pumps, liquid-contacting components, i.e., a pump body, a pump bellows, a suction side check valve, a discharge side check valve, and an accumulator bellows are made of a resin such as a fluororesin. In other pumps, also a pump cylinder and an accumulator cylinder which are non-liquid-contacting components are made of a resin, and a coupling shaft which is a metal component of a pump air chamber, and a flange and bolts which are used for coupling a pump bellows with the coupling shaft are covered with a resin, so that, even when the pump bellows or the accumulator bellows is broken, corrosion or metal ion efflux due to immersion does not occur.

SUMMARY OF THE INVENTION

In a conventional bellows pump, a flange and bolts are used for coupling a pump bellows with a coupling shaft. When several of the bolts are loosened or fastening torques of the bolts are uneven, the axis of the pump bellows is deviated from that of the coupling shaft, thereby causing the following problems. A sliding portion of the coupling shaft is unevenly worn, and therefore the life period of the pump is shortened. The sliding resistance is increased, and therefore the pump performance is lowered. Moreover, there is a fear that loosened bolts may slip off. In this case, the pump fails to normally operate. Furthermore, the numbers of components and assembly steps are increased, and the torques of fastening portions must be managed. Therefore, there are further problems such as that they may produce causes of impeding improvement of the productivity of the pump, and cost reduction.

Moreover, nuts and bolts are used in coupling of a coupling shaft with a piston or a coupling plate. Therefore, a gap is produced between the coupling shaft and the piston or the coupling plate by dimensional tolerances. This gap may cause the coupling shaft and the piston or the coupling plate to be fastened in a state where their axes are deviated from each other. Therefore, a sliding portion of the piston is unevenly worn, or the coupling plate obliquely applies a load to the coupling shaft, so that a sliding portion of the coupling shaft is unevenly worn, and the life period of the pump is shortened. The sliding resistance is increased, and therefore the pump performance is lowered. Moreover, there is a fear that loosened bolts may slip off. In this case, the pump fails to normally operate. Furthermore, the numbers of components and assembly steps are increased, and the torques of fastening portions must be managed. Therefore, there are further problems such as that they may produce causes of impeding improvement of the productivity of the pump, and cost reduction.

It is a first object of the invention to provide a bellows pump in which a shaft that is to couple a pump bellows with a piston or a coupling plate can be coupled with the pump bellows on the same axis without using a flange and a plurality of bolts, whereby the life period of the pump can be prolonged, the pump performance can be maintained for a long term, and compactification and cost reduction of the pump can be realized. It is a second object of the invention to provide a bellows pump in which a shaft that is to couple a pump bellows with a piston or a coupling plate can be coupled with the piston or the coupling plate on the same axis without using nuts and bolts in the piston or the coupling plate, whereby the life period of the pump can be prolonged, the pump performance can be maintained for a long term, and compactification and cost reduction of the pump can be realized.

The bellows pump of the invention is a bellows pump that comprises a pump bellows which axially extends and contracts, which sucks a transported liquid by extension of the pump bellows from a suction port of a pump body into the pump bellows via a suction side check valve, and which discharges the transported liquid by contraction of the pump bellows from a discharge port of the pump body via a discharge side check valve, wherein one end side of a shaft can be directly coupled with a center portion of the pump bellows by thread joining.

Specifically, the pump comprises a shaft which has an external thread on an external face on one side, the pump bellows has a bottomed cylindrical shape, and a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into the pump bellows on a same axis, and which has an internal thread on an inner face is disposed.

Preferably, a recess is disposed in a center portion of the pump body, and the shaft screwed portion has a length at which a tip end side of the shaft screwed portion is always fitted into the recess of the pump body.

When the pump bellows and the piston are to be coupled together by the shaft, preferably, an engagement head having a diameter which is larger than a diameter of the shaft is disposed in another end of the shaft, a center hole through which the shaft is to be passed in a center portion is disposed in the piston, the shaft is fitted into the center hole in a contracting direction of the pump bellows, and an annular sealing member which is made of an elastic material, such as an O-ring is attached to a portion of the shaft which is to be fitted into the center hole. Alternatively, the annular sealing member which is made of an elastic material may be attached to the center hole into which the shaft is to be fitted. More preferably, the center hole of the piston has a step which allows the other end of the shaft including the engagement head to be fitted into the hole.

When the pump bellows and the coupling plate are to be coupled together by the shaft, preferably, an engagement head having a diameter which is larger than a diameter of the shaft is disposed in another end of the shaft, a center hole through which the shaft is to be passed is disposed in a center portion of the coupling plate, the shaft is fitted into the center hole in a contracting direction of the pump bellows, and an annular sealing member which is made of an elastic material such as an O-ring is attached to a portion of the shaft which is to be fitted into the center hole. Alternatively, the annular sealing member which is made of an elastic material may be attached to the center hole into which the shaft is to be fitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing an internal structure of a bellows pump of a first embodiment of the invention;

FIG. 2 is an enlarged view of a pump unit of the bellows pump of FIG. 1;

FIG. 3 is a section view showing an internal structure of a bellows pump of a second embodiment of the invention;

FIG. 4 is an enlarged view of one of pump units shown in FIG. 3;

FIG. 5 is a section view showing an internal structure of a bellows pump of a third embodiment of the invention; and

FIG. 6 is an enlarged view of one of pump units shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings. FIG. 1 is a section view showing an internal structure of a bellows pump of a first embodiment of the invention, and FIG. 2 is an enlarged view of a pump unit shown in FIG. 1. The bellows pump 1 is used as a pump for transporting a liquid such as a chemical liquid, a solvent, or pure water in, for example, a semiconductor manufacturing factory, and is configured by: a pump body 4 which is a substantially square plate-like pump head, and in which suction and discharge ports 2 and 3 for the transported liquid are formed; a pump unit 5 which is placed on one side (the right side in FIG. 1) of the pump body 4; and an accumulator unit 6 which is placed on the other side (the left side in FIG. 1) of the pump body 4.

A pump bellows 7 which can extend and contract in the axial direction (the lateral direction in FIG. 1) is placed in one side portion (the right side portion in FIG. 1) of the pump body 4. The pump bellows 7 has a bottomed cylindrical shape which has a flange portion in an open edge. The flange portion forms an annular joining portion 8 in an open end portion, and is joined to the pump body 4, and the bottom portion configures a disk-like movable plate portion 9. The joining portion 8 and the movable plate portion 9 are integrally coupled with each other via a telescopic barrel portion 10 which has a cylindrical accordion-like structure. The pump bellows 7 and the pump body 4 form a cylindrical pump chamber (pump liquid chamber) 11 which is hermetically sealed, and which has a variable capacity. In the joining portion 8 of the pump bellows 7, a circular recess 12 is formed concentrically with the pump bellows 7 in a joining face with respect to the pump body 4, and, in the pump body 4, a circular projection 13 which is to be fitted into the recess 12 is formed concentrically with the pump body 4 in a joining face with respect to the joining portion 8 of the pump bellows 7. The recess 12 and the projection 13 which are fitted to each other hermetically seal between the joining faces of the pump bellows 7 and the pump body 4, and allow the pump bellows 7 to be placed on the same axis X as the pump body 4 while being positioned in a radial direction.

In one side portion (the right side portion in FIG. 1) of the pump body 4, a pump cylinder 14 which is a pump housing is further placed on the same axis X as the pump bellows 7. The pump cylinder 14 is configured by: a cylinder head portion 15 which is placed opposingly to the pump body 4 in the axially outside (the right outside of FIG. 1) of the pump bellows 7, and which has a substantially same shape as the pump body 4; a cylindrical first cylinder section 16 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the side of the pump body 4 (the left side of FIG. 1) so as to internally accommodate the pump bellows 7; and a cylindrical second cylinder section 17 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the side opposite to the first cylinder section 16 (the right side of FIG. 1). The first cylinder section 16 is opposed in an open end portion to the pump body 4 across the open end portion (the joining portion 8) of the pump bellows 7, and cooperates with the cylinder head portion 15 to form a pump air chamber 18 which is hermetically sealed, outside the pump bellows 7. A piston 19 is slidably fitted into the second cylinder section 17 in the axial direction (the lateral direction in FIG. 1). The open end portion of the second cylinder section 17 is closed by a cover 20 which is detachably attached by bolting. A circular center hole 21 is formed in the cylinder head portion 15. A pump shaft 22 which is placed on the same axis X as the pump bellows 7, and which is a shaft having a circular section slidably passes through the center hole 21 in the axial direction (the lateral direction in FIG. 1). The pump bellows 7 and the piston 19 are coupled together by the pump shaft 22.

In the pump body 4, a suction side check valve 24 which opens and closes a suction valve port 23 that communicates with the suction port 2 for the transported liquid, and a discharge side check valve 26 which opens and closes a discharge valve port 25 that communicates with the discharge port 3 for the transported liquid are mounted in the pump chamber 11. In the joining portion of the pump cylinder 14 with respect to the open end portion (the joining portion 8) of the pump bellows 7, i.e., the open end portion of the first cylinder section 16, an O-ring 27 which hermetically seals therebetween is attached to the portion. In the sliding portion of the pump cylinder 14 with respect to the pump shaft 22, i.e., the periphery of the center hole 21 of the cylinder head portion 15, an O-ring 29 which seals therebetween is attached to the portion via a slipper ring 28. In the sliding portion of the pump cylinder 14 with respect to the piston 19, i.e., the inner face of the second cylinder section 17, an O-ring 31 which seals therebetween is attached to the portion via a slipper ring 30. In order to reciprocate the pump bellows 7, a bellows-contraction air supply port 32 through which air is supplied to the pump chamber 18, and a bellows-expansion air supply port 33 through which air is supplied to the interior of the second cylinder section 17 on the side of the cylinder head 15 with respect to the attachment portion of the O-ring 31 are formed in the cylinder head portion 15 of the pump cylinder 14. A pair of proximity sensors 34, 35 which detect the extension/contract stroke end positions of the pump bellows 7 in the reciprocating operation of the piston 19 are attached to the second cylinder section 17 of the pump cylinder 14. Based on outputs of the proximity sensors 34, 35, an air supplying circuit which is provided between an air supply source (not shown) and the air supply ports 32, 33 is switched so as to alternatingly supply air to the pump chamber 11 and the second cylinder section 17. Namely, switching of steps of sucking and discharging the transported liquid by the bellows pump 1 is performed. The pump unit 5 is configured by the above-described components on one side portion (the right side portion in FIG. 1) of the pump body 4.

On the other hand, an accumulator bellows 36 which can extend and contract in the axial direction (the lateral direction in FIG. 1) is placed in the other side portion (the left side portion in FIG. 1) of the pump body 4. The accumulator bellows 36 has a bottomed cylindrical shape which has a flange portion in an open edge. The flange portion forms an annular joining portion 37 in an open end portion, and is joined to the pump body 4, and the bottom portion configures a disk-like movable plate portion 38. The joining portion 37 and the movable plate portion 38 are integrally coupled with each other via the telescopic barrel portion 39 which has a cylindrical accordion-like structure. The accumulator bellows 36 and the pump body 4 form a cylindrical accumulator chamber (accumulator liquid chamber) 40 which is hermetically sealed, and which has a variable capacity. The accumulator chamber 40 is communicatingly connected to the pump chamber 11 via the discharge side check valve 26 and a communication path 41 formed in the pump body 4, and communicates with the discharge port 3 formed in the pump body 4, so as to temporarily store the transported liquid that is discharged from the pump chamber 11 via the discharge side check valve 26. In the joining portion 37 of the accumulator bellows 36, a circular recess 42 is formed concentrically with the accumulator bellows 36 in a joining face with respect to the pump body 4, and, in the pump body 4, a circular projection 43 which is to be fitted into the recess 42 is formed concentrically with the pump body 4 in a joining face with respect to the joining portion 37 of the accumulator bellows 36. The recess 42 and the projection 43 which are fitted to each other hermetically seal between the joining faces of the accumulator bellows 36 and the pump body 4, and allows the accumulator bellows 36 to be placed on the same axis X as the pump body 4 while being positioned in a radial direction, so that it is placed on the same axis X as the pump bellows 7.

In the other side portion (the left side portion in FIG. 1) of the pump body 4, an accumulator cylinder 44 which is an accumulator housing is further placed on the same axis X as the accumulator bellows 36. In the accumulator cylinder 44 having a bottomed cylindrical shape, the bottom portion configures a cylinder head portion 45 which is placed opposingly to the pump body 4 in the axially outside (the left outside of FIG. 1) of the accumulator bellows 36, and which has a substantially same shape as the pump body 4, and the barrel portion configures a cylindrical cylinder section 46 which is projected so as to internally accommodate the accumulator bellows 36, from the cylinder head portion 45 to the side of the pump body 4 (the right side in FIG. 1) on the same axis X as the accumulator bellows 36. The cylinder section 46 is opposed in an open end portion to the pump body 4 across the open end portion (the joining portion 37) of the accumulator bellows 36, and cooperates with the cylinder head portion 45 to form an accumulator air chamber 47 which is filled with air for reducing pulsation, and which is hermetically sealed, outside the accumulator bellows 36. In the joining portion of the accumulator cylinder 44 with respect to the open end portion (the joining portion 37) of the accumulator bellows 36, i.e., the open end portion of the cylinder section 46, an O-ring 57 which hermetically seals therebetween is attached to the portion. A stopper 48 for restricting excess extending deformation of the accumulator bellows 36 to prevent the bellows from being broken is projected from the inner face of the accumulator cylinder 44. An automatic pressure adjusting mechanism 49 which is configured by an automatic air supply valve mechanism and an automatic air discharge valve mechanism, and which controls the air pressure in the accumulator air chamber 47 to balance with the discharge pressure of the pump unit 5 in accordance with variations of the pressure is attached to the accumulator cylinder 44. The accumulator unit 6 is configured by the above-described components on the other side portion (the left side portion in FIG. 1) of the pump body 4 on the same axis X as the pump unit 5.

The cylinder head portions 15, 45 which are on both the sides of the pump body 4 are fastened together with using plural metal tie rods 50 which are in parallel to the axis X, thereby configuring the bellows pump 1 in which the pump body 4, the pump unit 5, and the accumulator unit 6 are integrated. In this case, the tie rods 50 (including metal nuts 51 and the like on both the ends) are passed through and accommodated in flanges 52, 53, 54 which are formed on the outer faces of the pump body 4, the pump cylinder 14, and the accumulator cylinder 44, and which are joined together in series. Openings of both the ends of the accommodating portions are closed by detachable caps 55, 56, so as to prevent metal parts such as the tie rods 50 and the nuts 51 in both the ends from being corroded because of immersion. Alternatively, the pump body 4 is formed into a circular plate-like shape, an external thread is formed on both the side portions of the outer peripheral face, and nut portions which have on the inner face an internal thread to be screwed with the external thread are integrally formed in the open end portions of the cylinder sections 16, 46. The pump cylinder 14 and the accumulator cylinder 44 are directly coupled by means of thread coupling to both the ends of the pump body 4, respectively, thereby configuring the bellows pump 1 in which the pump body 4, the pump unit 5, and the accumulator unit 6 are integrated.

Next, the operation of the thus configured bellows pump 1 will be described. The suction port 2 of the pump body 4 communicates with the pump chamber 11 via a suction passage 2 a and the suction side check valve 24, the pump chamber 11 communicates with the accumulator chamber 40 via the discharge side check valve 26 and the communication path 41, and the accumulator chamber 40 communicates with the discharge port 3 of the pump body 4 via a discharge passage 3 a. In the pump unit 5, when air is supplied from the air supply source into the second cylinder section 17 through the air supply port 33 (at this time, the air supply port 32 is opened to the atmosphere), the pressure on the side of the cylinder head portion 15 becomes higher than that on the side of the piston 19 in the second cylinder 17. Therefore, the piston 19 moves toward the right side in FIG. 1, and, integrally with this movement, also the pump shaft 22 and the movable plate portion 9 of the pump bellows 7 move toward the right side in FIG. 1, or that is, the pump bellows 7 extends. As a result of the extending operation of the pump bellows 7, the suction side check valve 24 is opened, the discharge side check valve 26 is closed, and hence the transported liquid is sucked from the suction port 2 of the pump body 4 into the pump chamber 11 via the suction passage 2 a and the suction side check valve 24 (a suction step). Subsequently, air is supplied from the air supply source into the pump air chamber 18 via the air supply port 32 (at this time, the air supply port 32 is opened to the atmosphere), the pressure of the pump air chamber 18 is raised, and hence the pump bellows 7 contracts. As a result of the contracting operation of the pump bellows 7, the suction side check valve 24 is closed, the discharge side check valve 26 is opened, and therefore the transported liquid in the pump chamber 11 is discharged via the discharge side check valve 26. When the pump bellows 7 contracts, the pump shaft 22 and the piston 19 move integrally with this movement toward the left side in FIG. 1 (a discharge step). The above-described operations are repeated by a switching control of the steps of sucking and discharging the transported liquid, thereby performing a pump action.

On the other hand, in the accumulator unit 6, the accumulator chamber 40 receives via the communication path 41 the transported liquid discharged from the pump chamber 11, and the liquid is temporarily stored in the accumulator chamber 40, and then discharged from the discharge port 3 of the pump body 4 via the discharge passage 3 a. At this time, when the discharge pressure of the pump unit 5 is in a peak portion of the discharge pressure curve as a result of pulsation of the discharge pressure, the accumulator bellows 36 extends so as to increase the capacity of the accumulator chamber 40. The flow quantity of the transported liquid flowing out from the accumulator chamber 40 because of the extending operation becomes smaller than that of the flowing-in liquid. By contrast, when the discharge pressure comes to a valley portion of the discharge pressure curve, the discharge pressure becomes lower than the air filling pressure of the accumulator air chamber 47 which is compressed in accordance with the extension of the accumulator bellows 36, and hence the accumulator bellows 36 contracts so that the capacity of the accumulator chamber 40 is reduced. The flow quantity of the transported liquid flowing out from the accumulator chamber 40 because of the contracting operation becomes larger than that of the flowing-in liquid. The above-described operations are repeated in accordance with the steps of sucking and discharging the transported liquid by the pump unit 5, thereby performing a damper action.

Because of the pump action of the pump unit 5 and the damper action of the accumulator unit 6, the bellows pump 1 performs liquid transportation while sucking the transported liquid from the suction port 2 of the pump body 4, and continuously discharging the transported liquid from the discharge port 3 in an approximately constant flow quantity at a discharge pressure which is substantially smoothed as a result of absorption and attenuation of pulsation.

As apparent from the above description, in summary, the bellows pump 1 of the first embodiment comprises: the pump body 4 in which the suction and discharge ports 2 and 3 for the transported liquid are formed; the pump unit 5 which is placed on one side of the pump body 4; and the accumulator unit 6 which is placed on the other side of the pump body. The pump unit 5 comprises: the bottomed cylindrical pump bellows 7 which is placed so that the open end portion 8 is joined to the pump body 4 in one side portion of the pump body 4 to internally form the pump chamber 11, and which can axially extend and contract; the pump cylinder 14 configured by the cylinder head portion 15 which is placed opposingly to the pump body 4 in the axially outside of the pump bellows 7, the first cylinder section 16 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the pump body 4 so as to internally accommodate the pump bellows 7, which is opposed in the open end portion to the pump body 4 across the open end portion 8 of the pump bellows 7, and which cooperates with the cylinder head portion 15 to form the pump air chamber 18 outside the pump bellows 7, and the second cylinder section 17 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the side opposite to the first cylinder section 16, and into which the piston 19 is axially slidably fitted; the pump shaft 22 which slidably passes through a center portion of the cylinder head portion 15 in the axial direction to couple the pump bellows 7 with the piston 19; and the suction side and discharge side check valves 24 and 26 which are attached to the pump body 4 in the pump chamber 11. The pump bellows 7, the pump shaft 22, and the piston 19 are integrally reciprocated by air which is alternately supplied to the pump air chamber 18 and the second cylinder section 17. The pump bellows 7 repeatedly extends and contracts so that, when the pump bellows 7 extends, the transported liquid is sucked from the suction port 2 of the pump body 4 into the pump chamber 11 via the suction side check valve 24, and, when the pump bellows contracts, the transported liquid is discharged from the discharge port 3 of the pump body 4 via the discharge side check valve 26. By contrast, the accumulator unit 6 comprises: the bottomed cylindrical accumulator bellows 36 which is placed so that the open end portion 37 is joined to the other side portion of the pump body 4 to internally form the accumulator chamber 40 for temporarily storing the transported liquid that is discharged from the pump chamber 11 via the discharge side check valve 26, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder 44 which is placed outside the accumulator bellows 36, which is opposed in the open end portion to the pump body 4 across the open end portion 37 of the accumulator bellows 36, and which forms an accumulator air chamber 40 into which air is filled, outside the accumulator bellows 36. Pulsation of the discharge pressure of the pump unit 5 is absorbed by extension and contraction of the accumulator bellows 36.

Among the components of the bellows pump 1 of the first embodiment, in addition to the pump body 4, the pump bellows 7, the suction side check valve (including a valve case and a spring) 24, the discharge side check valve (including a valve case and a spring) 26, and the accumulator bellows 36 which are the liquid-contacting components of the pump unit 5 and the accumulator unit 6, also the pump cylinder 14, the piston 19, the pump shaft 22, and the accumulator cylinder 44 which are non-liquid-contacting components are made of a resin consisting of a resin material. Namely, the bellows pump 1 is made of a resin or resinified.

Preferable materials for resinification are as follows. With regard to the pump body 4, the pump bellows 7, the slipper rings 28, 30, the accumulator bellows 36, and the valve cases of the suction side check valve 24 and the discharge side check valve 26, a fluororesin such as PTFE (polytetrafluoroethylen) is preferably used. With regard to the valve elements and springs of the suction side check valve 24 and the discharge side check valve 26, a fluororesin such as PFA (polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) is preferably used. With regard to the pump cylinder 14, the cover 20, the accumulator cylinder 44, and the body 49 a of the automatic pressure adjusting mechanism 49, a resin such as PP (polypropylene) is preferably used. With regard to the pump shaft 22 and the piston 19, a resin such as PSP (polyphenylene sulfide) is preferably used. With regard to the caps 55, 56, a resin such as PE (polyethylene) is preferably used. The O-rings 27, 29, 31, 57 and all other O-rings which are used in the bellows pump 1 are made of fluoro rubber.

Next, a bellows pump of a second embodiment of the invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a section view showing an internal structure of the bellows pump of the second embodiment of the invention, and FIG. 4 is an enlarged view of one of pump units shown in FIG. 3. Also the bellows pump 58 is used as a pump for transporting a liquid such as a chemical liquid, a solvent, or pure water in, for example, a semiconductor manufacturing factory, and generally configured with disposing the pump unit 5 of the bellows pump 1 of the first embodiment in each side of the pump body 4. The components which are identical with those of the bellows pump 1 of the first embodiment are denoted by the same reference numerals, and their detailed description is omitted. Different portions will be described.

The bellows pump 58 of the second embodiment is configured by the pump body 4, and a pair of pump units 5 which are placed on both sides (the right and left sides in FIG. 3) of the pump body 4 on the same axis X, respectively. In each of the pump units 5, the piston 19 is formed to have a diameter which is larger than the outer diameter of the first cylinder section 16 of the pump cylinder 14, and, in accordance with this, also the second cylinder section 17 is formed to have a diameter which is larger than the outer diameter of the first cylinder section 16. The pistons 19 of the pump units 5 are fastened together by plural metal tie rods 59 which are in parallel to the axis X, in the radially outer side of the first cylinder sections 16. In each of the tie rods 59, steps 59 a, 59 b are formed in end portions, respectively. The steps 59 a, 59 b enable the pistons 19 of the pump units 5 to be coupled together with maintaining a predetermined distance between the pistons. The intermediate portions of the tie rods are slidably passed through and accommodated in flanges 60 in the axial direction (in the lateral direction in FIG. 3). The flanges are formed on the outer faces of the pump cylinders 14 of the pump units 5, and joined together in series. Small-diameter end portions which are outside the steps 59 a, 59 b are passed through the pistons 19, and projected toward the covers 20 for the pistons 19. Metal nuts 61 are screwed to the end portions of the tie rods 59 which are projected toward the covers 20 for the pistons 19. In the sliding portions of the flanges 60 with respect to the tie rods 59, i.e., the peripheries of openings of holes 62 on the side of the cylinder head portion 15, O-rings 64 which seal therebetween are attached to the portions via slipper rings 63, respectively. The tie rods 59 are passed through the holes 62. O-rings 66 hermetically seal between the tie rods 59 and hole 65 for the pistons 19.

The suction port 2 of the pump body 4 communicates with the suction valve ports 23 of the suction side check valves 24 of the pump units 5, and the discharge port 3 communicates with the discharge valve ports 25 of the discharge side check valves 26 of the pump units 5. Only the air supply port 33 through which air is supplied to the interior of the second cylinder section 17 on the side of the cylinder head 15 with respect to the attachment portion of the O-ring 31 is formed in each of the cylinder head portions 15 of the pump cylinders 14 of the pump units 5. A pair of proximity sensors 34, 35 are distributedly disposed in the pump units 5, and attached to the covers 20, respectively. The sensors are placed in positions where stroke ends of the pistons 19 along the extension direction of the pump bellows 7 are detected. Based on outputs of the proximity sensors 34, 35, an air supplying circuit which is provided between an air supply source (not shown) and the air supply ports 33 of the pump units 5 is switched so as to alternatingly supply air to the second cylinder sections 17 of the pump units 5. Namely, switching of steps of sucking and discharging the transported liquid by the bellows pump 58 is performed.

The bellows pump 58 in which the pump body 4 and the pair of the pump units 5 are integrated is configured by fastening the cylinder head portions 15 on both the sides of the pump body 4 with using the plural metal tie rods 50 which are in parallel to the axis X.

Next, the operation of the thus configured bellows pump 58 will be described. In the following description, the pump unit 5 on the left side in FIG. 3 is referred to as “left pump unit”, and the components of the left pump unit 5 are referred with affixing “left” to their names. By contrast, the pump unit 5 on the right side in FIG. 3 is referred to as “right pump unit”, and the components of the right pump unit 5 are referred with affixing “right” to their names. The suction port 2 of the pump body 4 communicates with the right and left pump chambers 11 via the right and left suction side check valves 24, and the right and left pump chambers 11 communicate with the discharge port 3 of the pump body 4 via the right and left discharge side check valves 26. When air is supplied from the air supply source into the left second cylinder section 17 through the left air supply port 33 (at this time, the right air supply port 33 is opened to the atmosphere), the pressure of the left cylinder head portion 15 becomes higher than that of the left piston 19 in the left second cylinder 17. Therefore, the left piston 19 moves toward the left side in FIG. 3, and, integrally with this movement, also the left pump shaft 22 and the movable plate portion 9 of the left pump bellows 7 move toward the left side in FIG. 3, or that is, the left pump bellows 7 of the left pump unit 5 extends. The extending operation of the left pump bellows 7 is transmitted from the left piston 19 to the right piston 19 of the right pump unit 5 via the tie rods 59. The right piston 19 moves toward the left side in FIG. 3, and, integrally with this movement, also the right pump shaft 22 and the movable plate portion 9 of the right pump bellows 7 move toward the left side in FIG. 3, or that is, the right pump bellows 7 of the right pump unit 5 contracts. As a result of this operation, the left suction side check valve 24 is opened, the left discharge side check valve 26 is closed, the right suction side check valve 24 is closed, and the right discharge side check valve 26 is opened. Therefore, the transported liquid is sucked from the suction port 2 of the pump body 4 into the left pump chamber 11 via the left suction side check valve 24 (a suction step of the left pump unit 5), and the transported liquid in the right pump chamber 11 is discharged from the discharge port 3 of the pump body 4 via the right discharge side check valve 26 (a discharge step of the right pump unit 5). Subsequently, when air is supplied from the air supply source into the right second cylinder section 17 through the right air supply port 33 (at this time, the left air supply port 33 is opened to the atmosphere), the pressure of the right cylinder head portion 15 becomes higher than that of the right piston 19 in the right second cylinder 17. Therefore, the right piston 19 moves toward the right side in FIG. 3, and, integrally with this movement, also the right pump shaft 22 and the movable plate portion 9 of the right pump bellows 7 move toward the right side in FIG. 3, or that is, the right pump bellows 7 of the right pump unit 5 extends. The extending operation of the right pump bellows 7 is transmitted from the right piston 19 to the left piston 19 of the left pump unit 5 via the tie rods 59. The left piston 19 moves toward the right side in FIG. 3, and, integrally with this movement, also the left pump shaft 22 and the movable plate portion 9 of the left pump bellows 7 move toward the right side in FIG. 3, or that is, the left pump bellows 7 of the left pump unit 5 contracts. As a result of this operation, the right suction side check valve 24 is opened, the right discharge side check valve 26 is closed, the left suction side check valve 24 is closed, and the left discharge side check valve 26 is opened. Therefore, the transported liquid is sucked from the suction port 2 of the pump body 4 into the right pump chamber 11 via the right suction side check valve 24 (a suction step of the right pump unit 5), and the transported liquid in the left pump chamber 11 is discharged from the discharge port 3 of the pump body 4 via the left discharge side check valve 26 (a discharge step of the left pump unit 5). The above-described operations are repeated by a switching control of the steps of sucking and discharging the transported liquid in the bellows pump 58, thereby performing a pump action.

Because of the above-described pump action in which the paired right and left pump units 5 alternately perform the suction step and the discharge step, the bellows pump 58 performs liquid transportation while sucking the transported liquid from the suction port 2 of the pump body 4, and discharging the transported liquid from the discharge port 3. When a single accumulator having a structure and function which are similar to those of the accumulator unit 6 of the bellows pump 1 of the first embodiment is added to the discharge side of the bellows pump 58, pulsation of the discharge pressure of the bellows pump 58 is absorbed and attenuated to be substantially smoothed, whereby liquid transportation can be continuously performed at an approximately constant flow quantity.

As apparent from the above description, in summary, the bellows pump 58 of the second embodiment comprises: the pump body 4 in which the suction and discharge ports 2 and 3 for the transported liquid are formed; and the pair of pump units 5 which are placed on both sides of the pump body 4, respectively. Each of the pump units 5 comprises: the bottomed cylindrical pump bellows 7 which is placed so that the open end portion 8 is joined to the pump body 4 in one side portion of the pump body 4 to internally form the pump chamber 11, and which can axially extend and contract; the pump cylinder 14 configured by the cylinder head portion 15 which is placed opposingly to the pump body 4 in the axially outside of the pump bellows 7, the first cylinder section 16 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the pump body 4 so as to internally accommodate the pump bellows 7, which is opposed in the open end portion to the pump body 4 across the open end portion 8 of the pump bellows 7, and which cooperates with the cylinder head portion 15 to form the pump air chamber 18 outside the pump bellows 7, and the second cylinder section 17 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the side opposite to the first cylinder section 16, and into which the piston 19 is axially slidably fitted; the pump shaft 22 which slidably passes through a center portion of the cylinder head portion 15 in the axial direction to couple the pump bellows 7 with the piston 19; and the suction side and discharge side check valves 24 and 26 which are attached to the pump body 4 in the pump chamber 11. The pistons 19 of the pump units 5 are coupled together, the suction valve ports 23 of the suction side check valves 24 of the pump units 5 are communicatingly connected to the suction port 2 of the pump body 4, and the discharge valve ports 25 of the discharge side check valves 26 are communicatingly connected to the discharge port 3. The pump bellows 7, the pump shafts 22, and the pistons 19 of the pump units 5 are integrally reciprocated in the same direction by air which is alternately supplied to the second cylinder sections 17 of the pump units 5. The pump bellows 7 of the pump units 5 repeatedly extend and contract in an alternate manner so that, when one of the pump units 5 sucks by extension of the pump bellow 7 the transported liquid from the suction port 2 of the pump body 4 into the pump chamber 11 via the suction side check valve 24, the other pump unit 5 discharges by contraction of the pump bellow 7 the transported liquid from the discharge port 3 of the pump body 4 via the discharge side check valve 26.

Also the bellows pump 58 of the second embodiment is resinified in the same manner as the bellows pump 1 of the first embodiment.

Next, a bellows pump of a third embodiment of the invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a section view showing an internal structure of a bellows pump of the third embodiment of the invention, and FIG. 6 is an enlarged view of one of pump units shown in FIG. 5. Also the bellows pump 67 is used as a pump for transporting a liquid such as a chemical liquid, a solvent, or pure water in, for example, a semiconductor manufacturing factory, and generally configured with disposing the pump unit 5 of the bellows pump 1 of the first embodiment in each side of the pump body 4, or that is, has the same structure as the bellows pump 58 of the second embodiment. The components which are identical with those of the bellows pump 58 of the second embodiment are denoted by the same reference numerals, and their detailed description is omitted. Different portions will be described.

The bellows pump 67 of the third embodiment is configured by the pump body 4, and a pair of pump units 5 which are placed on both sides (the right and left sides in FIG. 5) of the pump body 4 on the same axis X, respectively. In each of the pump units 5, the pump cylinder 14 is not provided with the second cylinder section 17. In accordance with this, the cover 20 is directly attached in a detachable manner to the cylinder head portion 15 by bolting to cover the piston portion, and the pistons 19 of the bellows pump 58 of the second embodiment are formed simply as disk-like coupling plates 68 which couple the pump shafts 22 of both the pump units 5 via the tie rods 59. Only the bellows-extension air supply port 32 for supplying air to the pump air chamber 18 is formed in the cylinder head portion 15 of the pump cylinder 14 of each of the pump units 5. Based on outputs of the proximity sensors 34, 35, an air supplying circuit which is provided between an air supply source (not shown) and the air supply ports 32 of the pump units 5 is switched so as to alternatingly supply air to the pump chambers 18 of the pump units 5. Namely, switching of steps of sucking and discharging the transported liquid by the bellows pump 67 is performed.

The bellows pump 67 in which the pump body 4 and the pair of the pump units 5 are integrated is configured by fastening the cylinder head portions 15 on both the sides of the pump body 4 with using the plural metal tie rods 50 which are in parallel to the axis X.

Next, the operation of the thus configured bellows pump 67 will be described. In the following description also, the pump unit 5 on the left side in FIG. 5 is referred to as “left pump unit”, and the components of the left pump unit 5 are referred with affixing “left” to their names. By contrast, the pump unit 5 on the right side in FIG. 5 is referred to as “right pump unit”, and the components of the right pump unit 5 are referred with affixing “right” to their names. The suction port 2 of the pump body 4 communicates with the right and left pump chambers 11 via the right and left suction side check valves 24, and the right and left pump chambers 11 communicate with the discharge port 3 of the pump body 4 via the right and left discharge side check valves 26. When air is supplied from the air supply source into the right pump air chamber 18 through the right air supply port 32 (at this time, the left air supply port 32 is opened to the atmosphere), the pressure of the right pump air chamber 18 is raised, and hence the right pump bellows 7 contracts. As a result of the contract operation of the right pump bellows 7, the right suction side check valve 24 is closed, and the right discharge side check valve 26 is opened. Therefore, the transported liquid in the right pump chamber 11 is discharged from the discharge port 3 of the pump body 4 via the right discharge side check valve 26 (a discharge step of the right pump unit 5). When the right pump bellows 7 contracts, the right pump shaft 22 and the right coupling plate 68 move integrally with this movement toward the left side in FIG. 5. The contracting operation of the right pump bellows 7 is transmitted from the right coupling plate 68 to the left coupling plate 68 of the left pump unit 5 via the tie rods 59. The left coupling plate 68 moves toward the left side in FIG. 5, also the left pump shaft 22 and the movable plate portion 9 of the left pump bellows 7 move integrally with this movement toward the left side in FIG. 5, or that is, the left pump bellows 7 of the left pump unit 5 extends. As a result of this operation, the left suction side check valve 24 is opened, and the left discharge side check valve 26 is closed. Therefore, the transported liquid is sucked from the suction port 2 of the pump body 4 into the left pump chamber 11 via the left suction side check valve 24 (a suction step of the left pump unit 5). Subsequently, when air is supplied from the air supply source into the left pump air chamber 18 through the left air supply port 32 (at this time, the right air supply port 32 is opened to the atmosphere), the pressure of the left pump air chamber 18 is raised, and hence the left pump bellows 7 contracts. As a result of the contracting operation of the left pump bellows 7, the left suction side check valve 24 is opened, and the left discharge side check valve 26 is closed. The transported liquid in the left pump chamber 11 is discharged from the discharge port 3 of the pump body 4 via the left discharge side check valve 26 (a discharge step of the left pump unit 5). When the left pump bellows 7 contracts, the left pump shaft 22 and the left coupling plate 68 move integrally with this movement toward the right side in FIG. 5. The contracting operation of the left pump bellows 7 is transmitted from the left coupling plate 68 to the right coupling plate 68 of the right pump unit 5 via the tie rods 59. The right coupling plate 68 moves toward the right side in FIG. 5, and also the right pump shaft 22 and the movable plate portion 9 of the right pump bellows 7 move integrally with this movement toward the right side in FIG. 5, or that is, the right pump bellows 7 of the right pump unit 5 extends. As a result of this operation, the right suction side check valve 24 is opened, and the right discharge side check valve 26 is closed. Therefore, the transported liquid is sucked from the suction port 2 of the pump body 4 into the right pump chamber 11 via the right suction side check valve 24 (a suction step of the right pump unit 5). The above-described operations are repeated by a switching control of the steps of sucking and discharging the transported liquid in the bellows pump 67, thereby performing a pump action.

Because of the above-described pump action in which the paired right and left pump units 5 alternately perform the suction step and the discharge step, the bellows pump 67 performs liquid transportation while sucking the transported liquid from the suction port 2 of the pump body 4, and discharging the transported liquid from the discharge port 3. When a single accumulator having a structure and function which are similar to those of the accumulator unit 6 of the bellows pump 1 of the first embodiment is added to the discharge side of the bellows pump 67, pulsation of the discharge pressure of the bellows pump 67 is absorbed and attenuated to be substantially smoothed, whereby liquid transportation can be continuously performed at an approximately constant flow quantity.

As apparent from the above description, in summary, the bellows pump 67 of the third embodiment comprises: the pump body 4 in which suction and discharge ports 2 and 3 for the transported liquid are formed; and the pair of pump units 5 which are placed on both sides of the pump body 4, respectively. Each of the pump units 5 comprises: the bottomed cylindrical pump bellows 7 which is placed so that the open end portion 8 is joined to the pump body 4 in one side portion of the pump body 4 to internally form the pump chamber 11, and which can axially extend and contract; the pump cylinder 14 configured by the cylinder head portion 15 which is placed opposingly to the pump body 4 in the axially outside of the pump bellows 7, and the first cylinder section 16 which is projected on the same axis X as the pump bellows 7 from the cylinder head portion 15 toward the pump body 4 so as to internally accommodate the pump bellows 7, which is opposed in the open end portion to the pump body 4 across the open end portion 8 of the pump bellows 7, and which cooperates with the cylinder head portion 15 to form the pump air chamber 18 outside the pump bellows 7; the pump shaft 22 which slidably passes through a center portion of the cylinder head portion 15 in the axial direction to couple one end with the pump bellows 7; the coupling plate 68 which is coupled with the other end of the pump shaft 22; and the suction side and discharge side check valves 24 and 26 which are attached to the pump body 4 in the pump chamber 11. The coupling plates 68 of the pump units 5 are coupled together, the suction valve ports 23 of the suction side check valves 24 of the pump units 5 are communicatingly connected to the suction port 2 of the pump body 4, and the discharge valve ports 25 of the discharge side check valves 26 are communicatingly connected to the discharge port 3. The pump bellows 7, the pump shafts 22, and the coupling plates 68 of the pump units 5 are integrally reciprocated in the same direction by air which is alternately supplied to the pump chambers 11 of the pump units 5. The pump bellows 7 repeatedly extend and contract in an alternate manner so that, when one of the pump units 5 sucks by extension of the pump bellow 7 the transported liquid from the suction port 2 of the pump body 4 into the pump chamber 11 via the suction side check valve 24, the other pump unit 5 discharges by contraction of the pump bellow 7 the transported liquid from the discharge port 3 of the pump body 4 via the discharge side check valve 26.

Also the bellows pump 67 of the third embodiment is resinified in the same manner as the bellows pump 58 of the second embodiment.

As apparent from the above description, each of the bellows pumps 1, 58, 67 of the first to third embodiments comprises the pump bellows 7 that axially extends and contracts, sucks the transported liquid by extension of the pump bellows from the suction port 2 of the pump body 4 into the pump bellows 7 via the suction side check valve 24, and discharges the transported liquid by contraction of the pump bellows from the discharge port 3 of the pump body 4 via the discharge side check valve 26. As seen from the corresponding figures of the bellows pumps 1, 58, 67, the pump bellows 7 and the pump shaft 22, or the pump shaft 22 and the piston 19 or the coupling plate 68, i.e., the three components of the pump bellows 7, the pump shaft 22, and the piston 19 or the coupling plate 68 which are integrally reciprocated are coupled together by the same coupling structure (method). The coupling structure will be described below.

First, the coupling structure of the pump bellows 7 and the pump shaft 22 in each of the bellows pumps 1, 58, 67 will be described. As enlargedly shown in FIGS. 2, 4, and 6, an external thread 69 is formed on the outer face (the outer face on the side of the pump bellows 7) of one end side of the pump shaft 22, so that the pump shaft 22 has a bolt structure. By contrast, in the bottomed cylindrical pump bellows 7, a bottomed cylindrical shaft screwed portion 70 is projected from a center portion of the bottom into the pump bellows 7 on the same axis X, an internal thread 71 which is to be screwed with the external thread 69 of the pump shaft 22 is formed on the inner face of the shaft screwed portion 70, and a shaft joint is integrated with a center portion of the pump bellows 7. According to the configuration, one end side of the pump shaft 22 can be directly coupled with a center portion of the pump bellows 7 by thread joining.

According to the coupling structure of the pump bellows 7 and the pump shaft 22, the pump shaft 22 is directly screwed into the shaft screwed portion 70 disposed in the center portion of the pump bellows 7, whereby the pump bellows 7 and the pump shaft 22 can be coupled and placed on the same axis X without using a flange and plural bolts. In this way, fastening parts are eliminated. Therefore, troubles due to loosening or slipping off of fastening parts can be prevented from occurring in the bellows pumps 1, 58, 67. That is, uneven wearing can be prevented from occurring in the sliding portion of the pump shaft 22, i.e., the periphery of the center hole 21 of the cylinder head portion 15, whereby the life period of the bellows pumps 1, 58, 67 can be prolonged, reduction of the performance of the bellows pumps 1, 58, 67 due to increase of the sliding resistance can be prevented from occurring, and the performance of the bellows pumps 1, 58, 67 can be maintained for a long term. Operation failures and damages of the bellows pumps 1, 58, 67 due to slipping off of a bolt are completely eliminated. The axial length of the bellows pumps 1, 58, 67 can be shortened by at least a dimension corresponding to that which is obtained by adding together the thicknesses of a flange and the head of a bolt. Therefore, compactification of the bellows pumps 1, 58, 67 can be realized. Moreover, improvement of the productivity of the bellows pumps 1, 58, 67, and reduction of the production cost can be realized by decrease of the number of components, and reduction of the number of assembly steps due to the decrease.

In the pump body 4, a circular recess 72 which has a diameter that is slightly larger than the outer diameter of the shaft screwed portion 70 of the pump bellows 7, and which has a depth that is larger than the extension stroke of the pump bellows 7 is formed concentrically in a center portion of the pump body. The shaft screwed portion 70 is formed so as to have a length at which the tip end side of the portion is always (not only when the pump bellows 7 contracts, but also when it extends) fitted into the recess 72 of the pump body 4. The tip end side of the shaft screwed portion 70 of the pump bellows 7 is always fitted into the recess 72 of the pump body 4.

According to the coupling structure of the pump bellows 7 and the pump shaft 22, compactification of the bellows pumps 1, 58, 67 can be realized while sufficiently ensuring the thread bonding strength between the pump bellows 7 and the pump shaft 22. Since the interior of the pump bellows 7, i.e., the center portion of the pump chamber 11 is filled with the shaft screwed portion 70, the total inner capacity of the pump bellows 7 (the capacity of the whole pump chamber 11) can be reduced so that the capacity ratio of the capacity of the accordion portion (the telescopic barrel portion 10: the portion exerting the pump action) to the total inner capacity of the pump bellows 7 (the capacity of the whole pump chamber 11) is increased. Therefore, the bellows pumps 1, 58, 67 can quickly start in the startup time, the discharge pressure is raised, and the performance of the bellows pumps 1, 58, 67 having the internal liquid structure can be improved.

Next, the coupling structure of the pump shaft 22 and the piston 19 or the coupling plate 68 in each of the bellows pumps 1, 58, 67 will be described. As enlargedly shown in FIGS. 2, 4, and 6, a circular engagement head 73 having a diameter which is larger than the diameter of the pump shaft 22 is integrally formed in another end of the shaft (the end on the side of the piston 19, or that on the side of the coupling plate 68). By contrast, a stepped center hole 74 into which the other end of the pump shaft 22 including the engagement head 73 can be fitted is formed in the piston 19 or the coupling plate 68. The center hole 74 is a stepped hole which has a circular section shape, and in which the hole diameter on one side (the side of the piston 19 or the coupling plate 68 on the side of the cylinder head portion 15) whit respect to a step face 75 is larger than that of the other side (the side of the piston 19 or the coupling plate 68 opposite to the cylinder head portion 15). The hole diameter of the small-diameter portion 76 is substantially equal to the outer diameter of the barrel portion of the pump shaft 22, and the hole diameter of the large-diameter portion 77 is substantially equal to the outer diameter of the engagement head 73 of the pump shaft 22. An annular sealing member which is used for filling a gap with respect to the center hole 74, and which is made of an elastic material, such as an O-ring 78 made of a fluororesin is attached to the pump shaft 22. The O-ring 78 is attached to a portion of the pump shaft 22 which is to be fitted into the small-diameter portion 76. According to the configuration, the other end side of the pump shaft 22 can be coupled with the center portion of the piston 19 or the coupling plate 68 by means of fitting. Alternatively, the O-ring 78 may be attached to the side of the center hole 74, i.e., the piston 19 or the coupling plate 68.

According to the coupling structure of the pump shaft 22 and the piston 19 or the coupling plate 68, the O-ring 78 is attached to the portion of the pump shaft 22 which is to be fitted into the center hole 74, or to the side of the hole 74, and fitted into the center hole 74 of the piston 19 or the coupling plate 68 in the contracting direction of the pump bellows 7, whereby the gap between the pump shaft 22 and the center hole 74 is filled with the O-ring 78, and the pump shaft 22 is radially positioned by the O-ring 78. Therefore, the pump shaft 22 and the piston 19 or the coupling plate 68 are not required to be fastened by bolts and nuts, and can be easily coupled together and placed on the same axis X. In this way, fastening parts are eliminated. Consequently, troubles due to loosening or slipping off of fastening parts can be prevented from occurring in the bellows pumps 1, 58, 67. That is, uneven wearing can be prevented from occurring in the sliding portion of the piston 19, i.e., the inner face of the second cylinder section 17. Furthermore, the coupling plate 68 can be prevented from obliquely applying a load to the pump shaft 22, and uneven wearing can be prevented from occurring in the sliding portion of the pump shaft 22, i.e., the periphery of the center hole 21 the cylinder head portion 15. Therefore, the life period of the bellows pumps 1, 58, 67 can be prolonged, reduction of the performance of the bellows pumps 1, 58, 67 due to increase of the sliding resistance can be prevented from occurring, and the performance of the bellows pumps 1, 58, 67 can be maintained for a long term. Operation failures and damages of the bellows pumps 1, 58, 67 due to slipping off of a bolt are completely eliminated. Moreover, improvement of the productivity of the bellows pumps 1, 58, 67, and reduction of the production cost can be realized by decrease of the number of components, and reduction of the number of assembly steps due to the decrease. Since the center hole 74 of the piston 19 or the coupling plate 68 is made as a stepped hole into which the other end of the pump shaft 22 including the engagement head 73 can be fitted, the axial length of the bellows pumps 1, 58, 67 can be shortened by at least a dimension corresponding to the thicknesses of the head of a bolt or a nut. Therefore, also compactification of the bellows pumps 1, 58, 67 can be simultaneously realized.

After the O-ring 78 is attached to the portion of the pump shaft 22 which is to be fitted into the center hole 74, or to the hole 74, the pump shaft 22 is passed through the center hole 74 of the piston 19 or the coupling plate 68 and the center hole 21 of the cylinder head portion 15 in the contracting direction of the pump bellows 7, the tip end side of the pump shaft 22 is inserted into the pump cylinder 14, and the inserted portion of the pump shaft 22 is directly screwed into the shaft screwed portion 70 of the pump bellows 7 until the tip end face of the pump shaft 22 butts against the bottom face of the shaft screwed portion 70, whereby, as shown in the figures, the three components or the pump bellows 7, the pump shaft 22, and the piston 19 or the coupling plate 68 can be coupled together and placed on the same axis X without using fastening parts.

In the double-bellows type bellows pumps 58, 67 of the second and third embodiments, a shaft stopper 80 which, when the pump bellows 7 contracts, prevents the pump shaft 22 from slipping off from the piston 19 or the coupling plate 68 is detachably attached to the outer side face of the piston 19 or the coupling plate 68. The shaft stopper 80 is made of the same resin material as the piston 19 or the coupling plate 68, and formed into a bottomed cylindrical shape. By contrast, an annular groove 81 into which the shaft stopper 80 can be fitted is concentrically formed around the center hole 74 in the outer side face of the piston 19 or the coupling plate 68. Threads 82 a, 82 b which are screwed with each other are formed in the outer peripheral face of the shaft stopper 80 and that of the corresponding groove 81. The shaft stopper 80 is thread-coupled with the groove 81 from the outer side face of the piston 19 or the coupling plate 68, closes the opening of the center hole 74 on the side of insertion of the pump shaft, causes the inner bottom face of the shaft stopper 80 to be in close contact with the engagement head 73 of the pump shaft 22, pressingly holds the engagement head 73 of the pump shaft 22 between the inner bottom face of the shaft stopper 80 and the step face 75 of the center hole 74, prevents the pump shaft 22 from slipping off from the piston 19 or the coupling plate 68 when the pump bellows 7 contracts, and transmits the extending operation of one of the pump bellows 7 to the other pump bellows 7 to cause the contracting operation. The shaft stopper is requested to prevent the pump shaft 22 from slipping off from the piston 19 or the coupling plate 68 when the pump bellows 7 contracts, and may have a structure other than the above-described structure. 

1. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, and one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining.
 2. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, and said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body.
 3. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed in a center portion is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 4. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed in a center portion is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 5. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a stepped center hole into which the other end of said shaft including said engagement head can be fitted is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 6. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a stepped center hole into which the other end of said shaft including said engagement head can be fitted is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 7. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a coupling plate which is coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passes is disposed in a center portion of said coupling plate, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 8. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, said bellows pump comprises a coupling plate which is coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed is disposed in a center portion of said coupling plate, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 9. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed in a center portion is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 10. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed in a center portion is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 11. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a stepped center hole into which the other end of said shaft including said engagement head can be fitted is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 12. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a piston which is to be coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a stepped center hole into which the other end of said shaft including said engagement head can be fitted is disposed in said piston, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 13. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a coupling plate which is coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed is disposed in a center portion of said coupling plate, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to a portion of said shaft which is to be fitted into said center hole.
 14. A bellows pump comprising a pump bellows which axially extends and contracts, said bellows pump sucking a transported liquid by extension of said pump bellows from a suction port of a pump body into said pump bellows via a suction side check valve, and discharging the transported liquid by contraction of said pump bellows from a discharge port of said pump body via a discharge side check valve, wherein said pump comprises a shaft which has an external thread on an external face on one side, said pump bellows has a bottomed cylindrical shape, a bottomed cylindrical shaft screwed portion which is projected from a center portion of a bottom into said pump bellows on a same axis, and which has an internal thread on an inner face is disposed, one end side of said shaft can be directly coupled with a center portion of said pump bellows by thread joining, a recess is disposed in a center portion of said pump body, said shaft screwed portion has a length at which a tip end side of said shaft screwed portion is always fitted into said recess of said pump body, said bellows pump comprises a coupling plate which is coupled with said pump bellows by said shaft, an engagement head having a diameter which is larger than a diameter of said shaft is disposed in another end of said shaft, a center hole through which said shaft is to be passed is disposed in a center portion of said coupling plate, said shaft is fitted into said center hole in a contracting direction of said pump bellows, and an annular sealing member which is made of an elastic material is attached to said center hole into which said shaft is to be fitted.
 15. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 3. 16. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 4. 17. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 5. 18. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 6. 19. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 9. 20. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 10. 21. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 11. 22. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; a pump unit which is placed on one side of said pump body; and an accumulator unit which is placed on another side of said pump body, said pump unit comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pump bellows, said shaft, and said piston being integrally reciprocated by air which is alternately supplied to said pump air chamber and said second cylinder section, said pump bellows repeatedly extending and contracting so that, when said pump bellows extends, the transported liquid is sucked from a suction port of said pump body into said pump chamber via said suction side check valve, and, when said pump bellows contracts, the transported liquid is discharged from a discharge port of said pump body via said discharge side check valve, said accumulator unit comprising: a bottomed cylindrical accumulator bellows which is placed so that an open end portion is joined to the other side portion of said pump body to internally form an accumulator chamber for temporarily storing the transported liquid that is discharged from said pump chamber via said discharge side check valve, and which can axially extend and contract; and a bottomed cylindrical accumulator cylinder which is placed outside said accumulator bellows, which is opposed in the open end portion to said pump body across said open end portion of said accumulator bellows, and which forms an accumulator air chamber into which air is filled, outside said accumulator bellows, pulsation of the discharge pressure of said pump unit being absorbed by extension and contraction of said accumulator bellows, said pump bellows, said shaft, and said piston of said pump unit being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 12. 23. A bellows pump according to claim 15, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 24. A bellows pump according to claim 16, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 25. A bellows pump according to claim 17, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 26. A bellows pump according to claim 18, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 27. A bellows pump according to claim 19, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 28. A bellows pump according to claim 20, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 29. A bellows pump according to claim 21, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 30. A bellows pump according to claim 22, wherein, in addition to said pump body, said pump bellows, said suction side check valve, said discharge side check valve, and said accumulator bellows which are liquid-contacting components of said pump unit and said accumulator unit, said pump cylinder, said piston, said shaft, and said accumulator cylinder which are non-liquid-contacting components are made of a resin material.
 31. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 3. 32. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 4. 33. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 5. 34. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 6. 35. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 9. 36. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 10. 37. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 11. 38. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across the open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows, and a second cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward a side opposite to said first cylinder section, and into which a piston is axially slidably fitted; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple said pump bellows with said piston; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said pistons of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said pistons of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said second cylinder sections of said pump units, said pump bellows of said pump units repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharges by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said piston of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said piston according to claim
 12. 39. A bellows pump according to claim 31, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 40. A bellows pump according to claim 32, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 41. A bellows pump according to claim 33, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 42. A bellows pump according to claim 34, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 43. A bellows pump according to claim 35, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 44. A bellows pump according to claim 36, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 45. A bellows pump according to claim 37, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 46. A bellows pump according to claim 38, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders, said pistons, and said shafts which are non-liquid-contacting components are made of a resin material.
 47. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, and a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across an open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple one end with said pump bellows; a coupling plate which is coupled with another end of said shaft; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said coupling plates of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said coupling plates of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said pump chambers of same pump units, said pump bellows repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharging by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said coupling plate of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said coupling plate according to claim
 7. 48. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, and a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across an open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple one end with said pump bellows; a coupling plate which is coupled with another end of said shaft; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said coupling plates of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said coupling plates of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said pump chambers of same pump units, said pump bellows repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharging by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said coupling plate of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said coupling plate according to claim
 8. 49. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, and a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across an open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple one end with said pump bellows; a coupling plate which is coupled with another end of said shaft; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said coupling plates of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said coupling plates of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said pump chambers of same pump units, said pump bellows repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharging by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said coupling plate of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said coupling plate according to claim
 13. 50. A bellows pump comprising: a pump body in which suction and discharge ports for a transported liquid are formed; and a pair of pump units which are placed on both sides of said pump body, respectively, each of said pump units comprising: a bottomed cylindrical pump bellows which is placed so that an open end portion is joined to said pump body in one side portion of said pump body to internally form a pump chamber, and which can axially extend and contract; a pump cylinder configured by a cylinder head portion which is placed opposingly to said pump body in an axially outside of said pump bellows, and a first cylinder section which is projected on a same axis as said pump bellows from said cylinder head portion toward said pump body so as to internally accommodate said pump bellows, which is opposed in an open end portion to said pump body across an open end portion of said pump bellows, and which cooperates with said cylinder head portion to form a pump air chamber outside said pump bellows; a shaft which slidably passes through a center portion of said cylinder head portion in an axial direction to couple one end with said pump bellows; a coupling plate which is coupled with another end of said shaft; and suction side and discharge side check valves which are attached to said pump body in said pump chamber, said coupling plates of said pump units being coupled together, suction valve ports of said suction side check valves of said pump units being communicatingly connected to said suction port of said pump body, discharge valve ports of said discharge side check valves being communicatingly connected to said discharge port, said pump bellows, said shafts, and said coupling plates of said pump units being integrally reciprocated in a same direction by air which is alternately supplied to said pump chambers of same pump units, said pump bellows repeatedly extending and contracting in an alternate manner so that, when one of said pump units sucks by extension of said pump bellow the transported liquid from said suction port of said pump body into said pump chamber via said suction side check valve, said other pump unit discharging by contraction of said pump bellow the transported liquid from said discharge port of said pump body via said discharge side check valve, said pump bellows, said shaft, and said coupling plate of each of said pump units being coupled together by said coupling structure of said pump bellows, said shaft, and said coupling plate according to claim
 14. 51. A bellows pump according to claim 47, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders and said shafts which are non-liquid-contacting components are made of a resin material.
 52. A bellows pump according to claim 48, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders and said shafts which are non-liquid-contacting components are made of a resin material.
 53. A bellows pump according to claim 49, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders and said shafts which are non-liquid-contacting components are made of a resin material.
 54. A bellows pump according to claim 50, wherein, in addition to said pump bodies, said pump bellows, said suction side check valves, and said discharge side check valves which are liquid-contacting components of said pump units, said pump cylinders and said shafts which are non-liquid-contacting components are made of a resin material. 